Calcification mechanisms will be studied using the statolith- synthesizing system of Aurelia. Intracellular nucleation vesicles of statocytes will be examined ultrastructurally to determine their site of origin. EM histochemical methods will be used to determine the chemical composition of the vesicles. In addition, efforts to decipher the mechanism of calcification of nucleation vesicles will involve the use of radioisotopes of calcium, sulfate, and phosphate. The effects of phosphate containing compounds (pyrophosphates, diphosphonates, cyclic AMP) as well as of hormones (thyroxine, PTH, CT, and GH) in statolith synthesis will be determined. Special attention will be paid to the possible roles of these compounds in affecting the uptake of ions, ion transportation in the statocytes and the mineralization of nucleation vesicles. An investigation of statolith growth in living intact jellyfish will be conducted using time-lapse cinematography. Information concerning the role of cells in mediating calcification processes, obtained from the jellyfish calcification model, will be applied to problems of calcification in bones and teeth of higher organisms, including man.